Stinging nettles give us an insight into both the capacity for nature to flourish even in some of the hardest urban conditions, and how plants are essential in providing us with some of the neccessities of life.

Not only do they provide excellent food for some butterflies and moths, but we can make tea from their leaves, use them as dyes, and once stung we will never forget their power to protect - as good a piece of environmental education as any.

Mathew FrithUrban Advisor, English Nature

Small Tortoiseshell - Aglais urticae

Perhaps the most well known of the nettle dependent butterflies - a frequent visitor to gardens in late summer.

The Small Tortoiseshell is one of our most common butterflies with an easily recognisable pattern of orange, yellow and black markings on the upper surface of the wings. A resident species it can be found across the whole of the British Isles including the more remote Scottish Islands.

The adults emerge from hibernation as soon as the days warm in spring and immediately set about feeding and breeding. The males will secure territories in a suitable sunny nettle patch each day. From here they chase any other butterfly that wanders past - the spiralling flight of rival males is a common sight over large nettle beds. Should a female fly past she is chased incessantly until the pair eventually land to mate within the nettle patch.

The female then concentrates on egg laying. Choosing the tender shoot tips of nettle at the edge of a large sunny bed she will lay a batch of about 80 eggs. These hatch about twelve days later. The army of tiny, black and yellow caterpillars immediately spin a silk tent around the nettle tips in which they can feed in relative safety. This continues with successively bigger, and very noticeable, tents until the caterpillars moult for the last time. At this point they become more less solitary and can exhibit leaf rolling tendencies like their relative the Red Admiral.

Those that survive parasitism may then wander many metres away from the nettle bed to pupate on tree trunks, walls and in hedgerows. The chrysalises vary from gold to brown in response to the pupation site. This camouflage attempt is not without reason for it is at this stage that a great many pupae are lost to hungry blue tits and other insect eating birds. Adults emerge from the pupae that remain in around twelve days.

The behaviour of these adults varies with the timing of their emergence. Those that emerge late in the year start to feed on nectar to build up fat reserves to see them through hibernation. Those that hatch early in the year set about breeding immediately and thus it is common to have two broods per year in the south of England or after a particularly warm spring. The adults from this second brood will then feed up for the winter - it is these adults we frequently see as they gorge themselves on our garden flowers.

Strangely enough the adults have come to exploit human endeavours in choosing their hibernation sites, frequently finding shelter in garden sheds and garages which are similar to their more natural tree hollow sites. If you do happen to be blessed with some winter visitors don't be tempted to move them as this will deplete their energy reserves and put them at risk.